Seoul, Sept 10 (AFP) North Korea on Tuesday fired projectiles toward the sea, South Korea's military said, hours after Pyongyang said it is willing to hold working-level talks with the United States in late September.

Negotiations between Pyongyang and Washington have been gridlocked since a second summit between the North's leader Kim Jong Un and US President Donald Trump in February ended without a deal.

North Korea twice launched "unidentified projectiles" Tuesday morning in an easterly direction from South Pyongan province, South Korea's Joint Chiefs of Staff said.

No further details were immediately available but these were the latest to be fired since July. Previous launches have been identified as short-range missiles.

"We are aware of reports of projectiles launched from North Korea," a senior US official said. "We are continuing to monitor the situation and consulting closely with our allies in the region."

Trump and Kim had agreed to restart working-level dialogue during an impromptu meeting at the Demilitarised Zone dividing the nuclear-armed North and South Korea in June, but those talks have yet to begin.

"We are willing to sit face-to-face with the US around late September at a time and place that we can agree on," Choe Son Hui, the North's vice foreign minister, said in a statement carried on Monday by the official Korean Central News Agency.

Choe's comment followed her warning in late August that North Korea's "expectations of dialogue with the US are gradually disappearing", after Pyongyang conducted weapons tests to protest joint US-South Korean military exercises.

Asked about the proposal for lower-level talks in September, Trump told reporters: "I have a very good relationship with Chairman Kim. I always say having meetings is a good thing. We'll see what happens."

The period suggested by North Korea would correspond with the United Nations General Assembly in New York.

On Monday, Choe recalled Kim's comments that the North would wait until the end of the year for Washington to "quit its current calculation method".

She repeated Pyongyang's call for the US to come up with an "acceptable calculation" or risk jeopardising the entire diplomatic process.

When asked by AFP about the latest North Korean offer, a State Department official replied: "We don't have any meetings to announce at this time."

Kim and Trump adopted a vaguely-worded statement on the "complete denuclearisation of the Korean peninsula" at their first summit in Singapore in June last year, but little progress has since been made on dismantling Pyongyang's nuclear programme.

A report published by a United Nations panel of experts last week said North Korea's development of nuclear warheads has not stopped, despite the moratorium it declared on nuclear blasts and long-range missile launches.

US officials have called North Korea's recent short-range missile launches provocations, although Trump himself has avoided criticising them.

Pyongyang is barred from ballistic missile tests under UN resolutions, and its previous short-range missile tests have been condemned by European members of the UN Security Council.

North Korea is under heavy US and UN sanctions over its weapons programmes, and has criticised Washington's position that sanctions against the isolated regime will not be lifted until the country gives up its nuclear weapons.

Pyongyang's latest comments on talks come after the US special envoy to North Korea, Stephen Biegun, said the North must stop blocking nuclear talks.

"If we are to succeed, North Korea must set aside its search for obstacles to negotiations and instead seek the opportunities for engagement while that opportunity lasts," he said on Friday.

"We have made clear to North Korea that we are prepared to engage as soon as we hear from them," he said on Friday. "We are ready, but we cannot do this by ourselves.